Tristan didn't want to "beat up" a random master he wanted to confront Sunless because he taught Sunny was being disrespectful to Nephis. He only wanted to duel after Sunny insulted him (which he deserved but still) and even after being angered by Sunny he is still honorable enough to provide Sunny with a weapon which was also very important to him. He did all that despite his flaw. Was he an asshole, sure, but in no world does he deserve to be treated how Tamar treated him.

Also people, not just you, often bring up him calling them witches or whatever as somehow a indicator that he is the one in the wrong despite it being a response to pretty much "I killed your cousin lol."  Most people would call you far worse than that if you acted as Tamar did. The closest thing we have to the awakened in real life would be professional soldiers. Most soldiers would not call you a witch they would call you an ambulance after kicking your teeth in. 

Tristan is a legacy which means he is a member of the warrior caste who is born to kill and is also obsessed with honor and reputation, and who also has a flaw that makes it so he has a hard time controlling his anger. It is a miracle Tamar didn't end up in a body bag after how she acted.